Version 1.21 of package Xr has just been released in GNU ELPA. You can now find it in M-x package-list RET.
Xr describes itself as: Convert string regexp to rx notation More at https://elpa.gnu.org/packages/xr.html Recent NEWS: Version 1.21: - Suppress false complaint about (? (+ X)) Version 1.20: - Fix duplication removal in character alternatives, like [aaa] - All diagnostics are now described in the README file - Improved anchor conflict checks Version 1.19: - Added filename-specific checks; new PURPOSE argument to `xr-lint' - Warn about wrapped subsumption, like \(A*C[AB]*\)+ - Improved scope and accuracy of all subsumption checks - Warn about anchors in conflict with other expressions, like \(A$\)B Version 1.18: - Fix test broken in Emacs 26 Version 1.17: - Performance improvements Version 1.16: - Translate [^\n] into nonl - Better character class subset/superset analysis - More accurate repetition subsumption check - Use text quoting for messages Version 1.15: - Warn about subsuming repetitions in sequence, like [AB]+A* Version 1.14: - Warn about repetition of grouped repetition Version 1.13: - More robust pretty-printing, especially for characters - Generate (category CHAR) for unknown categories Version 1.12: - Warn about branch subsumption, like [AB]\|A Version 1.11: - Warn about repetition of empty-matching expressions - Detect `-' not first or last in char alternatives or skip-sets - Stronger ad-hoc [...] check in skip-sets Version 1.10: - Warn about [[:class:]] in skip-sets - Warn about two-character ranges like [*-+] in regexps Version 1.9: - Don't complain about [z-a] and [^z-a] specifically - Improved skip set checks Version 1.8: - Improved skip set checks Version 1.7: - Parse skip-sets, adding `xr-skip-set', `xr-skip-set-pp' and `xr-skip-set-lint' - Ad-hoc check for misplaced `]' in regexps Version 1.6: - Detect duplicated branches like A\|A Version 1.5: - Add dialect option to `xr' and `xr-pp' - Negative empty sets, [^z-a], now become `anything' Version 1.4: - Detect overlap in character alternatives Version 1.3: - Improved xr-lint warnings Version 1.2: - `xr-lint' added
